1. Field of the Invention
The present invention relates to a water-based ball-point pen ink composition. More particularly, this invention relates to a water-based ball-point pen ink composition which shows shear-thinning properties.
2. Description of the Related Art
Agents for imparting shear-thinning properties have been disclosed which are to be added to water-based ink compositions for use in ball-point pens of the type in which when the ball-point pen is allowed to stand without imposition of shear stress on the ink, then the ink has a high viscosity and is stably held in the ball-point pen mechanism, and when the ball-point pen is in use for writing, then that part of the ink which is in the vicinity of the ball becomes less viscous due to the shear stress resulting from the ball rotation and is hence transferred to the paper surface. Examples of such prior art agents for imparting shear-thinning properties include water-dispersible gums and polysaccharides (see U.S. Pat. Nos. 4,545,818 and 5,466,283), organic polymeric compounds such as crosslinkable acrylic resins (see U.S. Pat. No. 5,767,172), inorganic compounds such as fine inorganic particles (see JP-A-6-256699; the term "JP-A" as used herein means an "unexamined published Japanese patent application"), and nonionic surfactants (see U.S. Pat. No. 5,785,746).